I would think that the lack of a combined report is perhaps something that could be solved by an Arquillian extension (if not in the long run, then certainly as a short term fix). That extension would tie into the report generation part of the lifecycle.

Jacoco in indeed the way to go: it provides coverage report without needing instrumentation and then without adding steps to build process. It is just about setting a -Djava.agent system property. No effect is visible on performance.

IMHO the best way to go for JBoss is to set up a Sonar instance (Sonar is a quality analysis and reporting tools, well integrated with Jacoco, Jenkins and Maven - able to report coverage, checkstyle, findbugs...). It is a really useful tools for developers and really helps in improving code and fighting technical debt.

Perhaps having even more weight than voting on the issue, there is an open GSoC proposal in the JBoss Community that involves fixing this plugin.

"Add a solution for creating series of snapshots of Java coverage data over time, so the developer can track the code coverage trends and have more information about the project. Currently the Jenkins plugin is not ready. I would like to make some improvements to bring the software to a more stable version and to finish the switching from the Emma plugin."

I've put in my vote for the project to move forward, but we'll find out if it makes the cut in a week or so.